1. Field of the Invention
The present invention relates to telephones. More specifically, the present invention relates to multiple handset cordless systems and wireless telephones.
2. Description of the Related Art
The field of telephony has changed dramatically since the break-up of AT&T in the early 1980's. Competition has driven innovation and the range of products available to consumers has increased accordingly. One area of innovation has been the development of cordless telephones. Cordless telephones are similar to conventional corded telephones in that they are connected by wire to a local central office. However, they differ in that there is no cord between the base unit of the cordless telephone and the handset; thus, they are called ‘cordless’ telephones. Cordless telephones add the convenience of mobility within the range of coverage of the radio transceivers employed in the base and handset units that comprise the cordless telephone.
The deployment of cellular service established the beginning of a wireless telephony era. The first widely adopted and implemented standard in the United States was AMPS cellular. Later, other standards were implemented, including TDMA (IS-136), CDMA (IS-95), GSM, PCS (various standards), and others. All of these wireless telephones share the characteristic in that there is no local metallic loop between the telephone and a telephone company central office employed to render service. Rather, a wireless telephone network is deployed by a service provider, and wide area coverage (at least respecting the coverage range of a cordless telephone) is delivered via radio signals. Wireless telephones do not typically comprise a base unit; rather, the entire telephone circuitry is inside a single enclosure, including the battery.
Wireless telephones do suffer from certain disadvantages. They are physically small, and hence the user interface is rather compact and reduces the convenience of operation. The transmitter power and received signal strengths are very low, due to the battery power limitations and network infrastructure considerations. This means that radio signal strength is often time so limited that interference and noise become common annoyances during calls. The mobility of the receiver exacerbates this because of the vagaries of radio propagation, including multi-path interference, Rayleigh fading, and physical blocking of radio signal paths. In addition, wireless telephones have limited battery life, especially during extended conversation times.
Cordless telephones offer improved interfaces and performance over wireless telephones in most circumstances. They are usually larger and have more complete and convenient user interfaces. The base unit can house voice messaging systems and speakerphones. They operate in a small geographic area so that signal levels at the receivers of both the base and handset are higher, offering better receiver quieting, higher signal to noise ratios, and less interference generally. They also offer longer battery life standby and talk times, owing to their larger batteries and their more extended times at rest on a charging cradle. Recently, manufacturers of cordless telephones have developed multiple handset cordless telephone systems. A multiple handset system typically employs a base unit and multiple handsets. Handsets are able to communicate between each other as an intercom, in addition to communicating with the base unit for interconnectivity with the public switch telephone network. Multiple handset cordless systems may operate in various frequency bands, 900 MHz, 2.4 GHz and others. The communications protocol used in multiple handset cordless systems may be proprietary or follow a promulgated standard, such as the Bluetooth standard, known to those skilled in the art.
The trend for many users of wireless telephones is toward using their wireless telephone as the principal communications device, even over the traditional wired and corded telephones. Users merely keep their wireless telephone with them at all times, whether during travel, at home, or at work. Thus, they are readily reachable by calling to the wireless telephone number. However, this implies the aforementioned limitations of wireless telephones are always present for such users. It is known in the art to utilize a base unit with a wireless telephone that offers battery charging, hands free operation, and even interfaces to RJ-11 devices, such as wired telephones. However, such devices are cumbersome to use, limit mobility, and may require installation procedures beyond the skill level of average users. The tension between wireless telephones and cordless telephones was mitigated with an invention that integrated a cordless telephone base unit with a wireless telephone docking cradles, and the interconnection of communications signals therebetween. See U.S. patent application Ser. No. 09/737,289 filed on Dec. 13, 2000, to Uchiyama and entitled Cordless and Wireless Telephone Docking Systems. With the deployment of multiple handset cordless telephones, which offer even greater conveniences, the tension between the mobility of wireless telephones and convenience of wireless telephones has increased. Thus, there is a need in the art for an integration apparatus and method to improve upon the utilization of a wireless telephone in a local geographic area while maintaining mobility through the use of cordless telephony technology having multiple handset capabilities and features.